In material tests utilizing RF resistance heating, an RF transformer is often required as a current step-up between the generating means and the load. With prior art practice, it has been possible to precisely match a load only by having available multiple transformers, though approximate matching has been possible with low-coupling-coefficient multiple-tapped transformers. To obtain a high current step-up ratio, a high coupling coefficient is needed between the secondary and primary. Prior art transformers have a relatively large uniform gap between the primary and secondary to prevent damage from electric arcs formed between the primary and secondary. This large spacing results in a low coupling coefficient. Further, the round tubing used for the primary in such RF transformers suffers from large resistance losses due to the proximity effect.
It is therefore an object of this invention to provide an improved RF transformer.
Another object of this invention is to provide an RF transformer with a high coupling coefficient.